1. Field of the Invention
The present invention relates to a photographic processor comprising a negative film supply section for conveying and supplying a negative film and an exposure section for printing an image frame of the negative film conveyed and supplied from the negative film supply section onto a printing paper. In particular this invention relates to the technology for positioning the negative film in the photographic processor.
2. Discussion of the Related Art
In a conventional photographic processor to print an image frame onto printing paper by the use of a negative film, a notch punched on the negative film has been used for positioning the image frame of the negative film in a film reading device to scan each image frame for obtaining a corrected exposure condition and in an exposure device to expose the printing paper to light through each image frame. Before the negative film is mounted on the photographic processor, this notch is punched in the vicinity of each image frame by a notch punching device such as is disclosed in Japanese Patent Laid-Open Publication No. 184036/1991.
As described above, after a developed negative film is mounted on the notch punching device and the notches are punched in it for positioning, the negative film is rewound and dismounted from the notch punching device. Then the negative film is installed into the negative film supply section of the photographic processor. Consequently, these complicated processes make it difficult for the negative film to be processed consecutively in a continuous manner. Therefore, instead of using the notches, for positioning the negative film in the photographic processor, another technology is proposed to confirm a configuration of the image frame by a detected signal from a picture sensor for positioning the negative film. This technology allows the elimination of punching a number of notches in the negative film so that the processing of the negative film can be continuous. However, all of the image frames on the negative films do not have configurations clear enough to be automatically detected by the picture detecting sensor. In the case they are not clear enough, the negative film should be positioned by another method. For example, an image frame with an unclear configuration can be positioned by using a picture with a clear configuration, taking it as a reference point and then feeding the negative film a predetermined amount from that clear image. This method works when there is such an image frame nearby that is clear enough to be used for positioning by the picture detecting sensor. However, when the image frame with an unclear configuration is a certain distance away from that image frame with a clear configuration, it is difficult to stop the negative film accurately at its expected position due to the margin of error in the amount the negative film is fed. To solve this problem, an operator must visually position the image frame which has an unclear configuration as described above. This prevents the photographic processor from working with a high operating efficiency because the photographic processing includes many processing portions in which the negative film should be positioned and these include the film reading portion, an exposure portion, a cutting portion to cut into a piece of negative film and so on.